The present invention relates generally to apparatus for producing an electrical pulse in response to each actuation of a double throw electromechanical switch, and more particularly, to such apparatus for alternately producing pulses of electric current in opposite directions in response to successive opposing actuations of a double throw electromechanical switch, such pulses being suitable for controlling the state of a transformer relay.
The desirability of controlling the light output of fluorescent lighting fixtures for energy conservation and other reasons is well recognized. Partially for this purpose, fluorescent lighting fixtures are frequently provided with electronic dimming ballasts whose construction and operation are well known, and whose control requirements have become largely standardized. A relatively typical electronic ballast has four electrical input leads, of which two are alternating current (AC) power leads, and two are for connection to a device for providing dimming control signals. The color convention for the leads is white and black for the power leads and violet and gray for the control leads.
The electronic ballast is designed such that the energization which it supplies to fluorescent lamps connected thereto is effectively determined by the value of an impedance connected between the control leads. A short circuit between the control leads, resulting in a zero voltage therebetween, causes the lamps to be off. Impedances between the control leads which result in voltages between 1.5 and 9 volts cause the lamps to be on at an output level proportional to the voltage. Power to the ballast and lamps may be completely turned off by a separate switch or relay contacts in the black power lead.
A variety of devices are commercially available for effectively providing an impedance which is variable over the requisite range of values for controlling an electronic ballast. A circuit diagram for such a device is shown in the lower portion of FIG. 4. This diagram specifically represents the circuit used in Model EL7315 and Model EL7316 Electronic Ballast Manual Dimmers commercially available from Honeywell Inc.
As shown, the circuit includes a manually controlled variable resistor, and an ON-OFF switch formed by one section of a two pole, double throw switch. This circuit is operable, depending on the position of the manual controls, to provide an impedance which is at zero or variable between predetermined limits. In particular, if the ON-OFF switch is in the ON position, the impedance is determined by the variable impedance element. If the ON-OFF switch is in the OFF position, it provides a short circuit between violet and gray leads of the circuit. A switch separate from the Dimmer is required to completely shut off power to ballast and lamps.
Another device capable of controlling both the primary power to an electronic ballast and the dimming control signal required thereby is a remote relay control box, such as a Model EL7305 Electronic Ballast Controller, also commercially available from Honeywell Inc., and described in detail in U.S. Pat. Nos. 5,004,972 and 5,028,862 issued to R. Roth on Apr. 2, 1991 and Jul. 2, 1991, respectively. The EL7305 Controller includes four output leads for connection to the four input leads of an electronic ballast for providing both primary power and dimming control thereto. The EL7305 Controller also includes a pair of input leads for connection to the EL7315 or EL7316 Dimmer, and responds to signals therefrom by cutting off power to the electronic ballast if the ON-OFF switch is in the OFF position. If the ON-OFF switch is in the ON position, the Dimmer presents a variable impedance between the violet and gray leads for varying the light output of the fluorescent lamps. Thus, a separate manually operated switch is not required for complete control.
EL7305 Controllers, additionally, are capable of being interconnected to provide lighting control for large areas, and of accepting other input signals, such as provided by occupancy sensors. Because of these expanded capabilities, the EL7305 Controller is relatively expensive.
Another well known device for controlling power to a load, such as a fluorescent lighting fixture, from a remote momentary switch is a transformer relay. This device combines a transformer and relay into a single structure, thus reducing manufacturing and installation costs. Specifically, a transformer relay is a magnetic latching relay which can be operated remotely from a low voltage, momentary, wall mounted switch. One supplier of relatively typical transformer relays for lighting circuits is Enercon Data. These transformer relays have five electrical leads including white and black power leads, yellow and brown control leads, and a blue load lead for connection, in the case of a fluorescent lighting fixture, to the black primary power lead of the electronic ballast.
Such a prior art transformer relay is schematically illustrated in FIG. 1 along with a basic control circuit which includes a momentary single pole, double throw switch and a pair of steering diodes. Switching of the relay is accomplished by momentarily connecting a diode between the yellow and brown control leads. If the leads are connected through a diode with the cathode connected to the yellow lead, the relay supplies power to the load. If the leads are connected through a diode with the cathode connected to the brown lead, the relay switches OFF power to the load. Only a pulse is needed to change the state of the relay.
It is apparent from the preceding background discussion that a single wall unit capable of (1) providing direct input to a ballast dimmer to change the power level to a fluorescent lamp, or (2) providing the requisite inputs to a remote relay control box to achieve changes in power level and turn power ON or OFF, or (3) providing inputs to a ballast dimmer to vary the power level and to a transformer relay to turn power ON or OFF would be advantageous. Since a remote relay control box is considerably more expensive than a transformer relay, having the option to provide ON-OFF control from a single wall unit through a transformer relay in appropriate situations would also be advantageous.